Earlier today, Australian authorities said they may have a signal from the missing Malaysian airliner that disappeared a month ago on its way to Beijing. A ship far out in the Indian Ocean has picked up a signal that could be from the missing airliner's black boxes. Investigators need those boxes to determine what happened to Malaysian Air Flight 370.

And joining me now in the studio now is NPR science correspondent Geoff Brumfiel, who's been closely following the search. Hello there, Geoff.

GEOFF BRUMFIEL, BYLINE: Hello.

CORNISH: So this has been described as a ping. Tell us more about the signal.

BRUMFIEL: Well, this is an acoustic signal that was heard by an Australian ship that was combing a predefined search area hundreds of miles off the coast. And the signal was at a frequency that's too high for the human ear to hear. But a company called Dukane systems that makes his pingers supplied us with an audible version. Here it is.

(SOUNDBITE OF PINGS)

CORNISH: All right, sounds pretty simple. I mean, a kind of clicking or like a metronome.

BRUMFIEL: Exactly. And, I mean, that's the thing about the signal. It's a very simple single. It's nothing fancy and there's a good reason for that, because these pingers are attached to the airplanes to black boxes. They're supposed to sit on these black boxes for years. And then when the airplane goes down, if that should happen to happen, they're supposed to turn on when they come in contact with water, and then ping consistently one second at a time for 30 days.

And so, they are looking for reliability over anything too fancy - just something that'll work - a battery, a little transducer and not much else.

CORNISH: So, what are the chances, though, that it could be something else?

BRUMFIEL: I spoke to Anish Patel, who's president of Dukane, the company that makes these pingers, as they're called. And he actually heard an audio file of the real Australian signal over the weekend. Here's how he described it.

ANISH PATEL: It had a one-second pulse rate which matches the typical pinger rate. The frequency was shifted a little bit lower than we usually see in these pingers, but that could be for a host of reasons. So it very much sounded like a standard beacon ping when you hear it converted to an audible range.

BRUMFIEL: And I spoke to some oceanographers, as well. And they told me that this stretch of Indian Ocean is one of the quieter places on earth. There's not a lot of shipping noise or other human noise. The only thing that could make something similar is may be a marine mammal like a dolphin. But these pings went on for more than two hours. And it's very unlikely a dolphin is going to click at a one-second interval for more than two hours. So it looks like this could really be it.

CORNISH: OK, but I understand that at some point they actually lost the signal.

BRUMFIEL: Yeah, that's right. They have actually lost the signal. So they listen to it for two hours and then they lost it. And then they got another signal for a few minutes and they lost it again. And what you have to understand is that trying to hear the signal is really, really hard. This search area is nearly three miles beneath the surface of the ocean, and sound travels in very funny ways.

There can be sort of a shimmering effect, like if you look at a mirage off on the horizon you can't see it very clearly. Well, sound waves can be distorted, they can be reflected, so they really have a big job trying to get the signal back.

If they can, what they'd like to do is reacquire it in several different locations, and then use that to triangulate where they think it's actually coming from. But they have to do that pretty quickly because these pingers only last for about 30 days, and it's pretty much 30 days now. They may have five or six day's leeway. But towards the end of the week, the battery power will run out.

CORNISH: Now, once they do that what will they do? What's the next step?

BRUMFIEL: Well, you can't send a submarine down there because it's too deep. So what they're likely to do is send underwater automated vehicles. The first ones they'll send, there's one they have on board called Bluefin 21. It uses sonar to try and identify the location of the wreckage. Later on, if they can actually find it, they'll probably send unmanned vehicles with cameras and eventually, hopefully, even claws so that they can find the black boxes.

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